An accurate and cost-effective COG defuzzifier without the multiplier and the divider

This paper proposes an accurate and cost-effective COG defuzzifier of fuzzy logic controller (FLC). The accuracy of the proposed COG defuzzifier is ob tained by involving both membership values and spans of membership function s in calculating a crisp value. The cost-effectiveness of the proposed COG defuzzifier is obtained by finding the moment equilibrium point instead of computing the division in the COG defuzzifier. The proposed COG defuzzifier has two disadvantages: it increases the hardware complexity due to the add itional multipliers and it takes a lot of computation time to find the mome nt equilibrium point. The first disadvantage is overcome by replacing the m ultipliers with the stochastic AND operations. The second disadvantage is a lleviated by using a coarse-to-fine searching algorithm that accelerates th e finding of moment equilibrium point by O(M) maximally when compared with the equal interval searching method of Ruiz et al. (1995). Application of t he proposed COG defuzzifier to the truck backer-upper control problem is pe rformed in the VHDL simulation and the control accuracy of the proposed COG defuzzifier is compared with that of the conventionally simplified COG def uzzifier in terms of average tracing distance. (C) 1999 Elsevier Science B. V. All rights reserved.